Already own an Apexi RSM (Rev/Speed Meter) and want to add a bigger shift lamp? You’re not alone. Many car enthusiasts look for a more visible RPM shift indicator, especially when pushing their cars on the street or track. Fortunately, the Apexi RSM provides a useful output signal that makes this DIY mod possible.
In this guide, I’ll show you how to wire a relay using the RPM signal from your Apexi RSM to power a larger shift lamp. It’s simple, satisfying, and highly functional.
What is the Apexi RSM?
The Apexi RSM, or Rev/Speed Meter, is a multifunctional device that monitors various engine and speed parameters. Originally designed to pair with other A’PEXi electronics like the V-AFC and AVC-R, it has become a favorite among JDM car enthusiasts.
Standard features include:
- RPM and vehicle speed display
- Real-time graphs and analog/digital readouts
- Peak hold and replay (up to 60 seconds)
- Speed limiter cut function
- 0–100m, 200m, and 400m timings
- Mid-range acceleration and stopwatch features
- RPM and speed output signals for external devices
- Tire size correction and weight input
This versatility makes the Apexi RSM perfect for adding external devices like shift lamps.
Wiring the Shift Lamp Using Apexi RSM
To connect a bigger shift lamp, we’ll be using a basic automotive relay. This setup ensures the signal from the Apexi RSM properly triggers your external shift lamp without overloading the unit.
Relay Pinout & Wiring
- Signal from Apexi RSM (RPM output) = Pin 86
- Ground (connect to chassis or clean metal surface) = Pin 85
- Positive (+12V from battery or ignition) = Pin 30
- Output to your shift lamp = Pin 87
When the RSM sends the shift signal, the relay closes, and power flows to your custom shift lamp.
This setup ensures your lamp only lights up at your desired RPM, just like a pro-level setup—without needing a full standalone ECU.
Why This Mod Works
Many aftermarket shift lamps require a clean and reliable RPM signal to function accurately. The Apexi RSM provides just that. By tapping into its RPM output, you skip the complexity of tapping into the ignition coil or ECU harness directly. This results in faster response and a cleaner install.
Additionally, using a relay protects your RSM from current overload and allows flexibility in lamp choice—from LED strips to full-size tach lights.
Final Thoughts
With just a few wires and a basic relay, you can enhance your driving experience using the Apexi RSM as your RPM signal source. Not only does it look cool, but it also gives you a more effective way to monitor your engine’s revs.
Want more DIY tuning content or need help with other RSM features? Drop your questions in the comments or message me directly!
